DEVELOPMENTS IN SHORT-WAVE DIRECTIVE ANTENNAS 665 



large economic saving could be effected. Development work was 

 undertaken which has not only resulted in an antenna of considerable 

 frequency latitude, but this new antenna structure is actually less ex- 

 pensive than a single, equally effective unit of the previous type. The 

 remainder of this paper will be devoted to a discussion of various ap- 

 plications of this form of antenna. 



Principles of "Tilted" Wire Antennas 

 The elementary principles underlying "tilted" wires can be ex- 

 plained more readily by presenting a physical picture, through the use 

 of r-m-s vector representation, rather than through a more or less cum- 

 bersome mathematical treatment. The vector representations that 

 follow are not rigorous but they serve to convey quickly the ideas under 

 consideration and give results which are in sufficiently good accord with 

 the complete mathematic analysis. 



As we increase the length of a simple vertical antenna exposed to 

 horizontally propagated waves, always rematching impedances by 

 varying the load at its base, we obtain increases in the load power up to 

 the point where the antenna wire length reaches one-half wave-length. 

 The vector representation of this one-half wave-length case constitutes 

 Fig. 6. 



/ 



\ 



WAVE 



\ 



/ 



PERFECT GROUND 



RESULTANTS > 



NOTE : COUNTER CLOCKWISE ROTATION WITH 

 ADVANCING PHASE IS EMPLOYED 



Fig. 6— Vector relations in a half- wave vertical antenna. 



